In the 5 th millennium B.C., the Greek philosophers Plato and Aristotle believed that animals and plants form a single, graded continuum going from more perfection to less perfection. Humans, of course, were at the top of this scale.

Later Greek philosophers added the idea that the creator gave life or “radiance” first to humans, but at each subsequent creation some of that essence was lost.

The attentive observer will discover a connection of parts, from the Supreme God down to the last dregs of things, mutually linked together and without a break. Homer’s golden chain, which God, he says, bade hand down from heaven to earth.

All things were linked to each other in a chain, and all links were necessary. Belief in the chain of being was accompanied by the conviction that an animal or plant species could not become extinct.

Early in the 18 th century, an influential scientist classified plants and animals in a systema naturae, which placed humans in the same order (Primates) as apes and monkeys. Linnaeus did not suggest an evolutionary relationship between humans and apes; he mostly accepted the notion that all species were created by God and fixed in their form.

Not surprisingly, then, linnaeus is often viewed as an anti-evolutionist. Linnaeus’s hierarchical classification scheme, in descending order going from Kingdom to class, order, genus (a group of related species), and species, providing a framework for the idea that humans, apes, and monkeys had a common ancestor.

According to Lamarck acquired characteristics could be inherited and therefore species could evolve.

Individuals who in their lifetime developed characteristics helpful to survival would pass those characteristics to future generations, therefore changing the physical makeup of the species. For example: Lamarch explained the long neck of the giraffe as a result of successive generations of giraffes stretching their necks to reach the high leaves of trees. The stretched muscles and bones of the neck were somehow transmitted to the offspring of the neck-stretching giraffes, and eventually all giraffes came to have long necks.

But because Lamarck and later biologists failed to produce evidence to support the hypothesis that acquired characteristics can be inherited, this explanation of evolution is now generally dismissed.

Leading opponent of evolution. Cuvier’s theory of catastrophism proposed that a quick series of cataclysms accounted for changes in the earth and the fossil records. Cataclysms and upheavals such as Noah’s flood had killed off previous sets of living creatures, which each time were replaced by new creatures.

Geologist James Hutton ( ) questioned catastrophism, but his work was largely ignored. Sir Charles Lyell ( ) published Principles of Geology ( ) which built on Hutton’s earlier work, received immediate acclaim.

Their concept of uniformitarianism suggest that the earth is constantly being shaped and reshaped by natural forces that have operated over a vast stretch of time. Lyell also discussed the formation of strata and paleontology. He used fossilized fauna to define different geological epochs.

Darwin rejected the notion that each species was created at one time in a fixed form. He believed that that animals and plants evolved through the mechanism of natural selection. Charles Darwin’s theory of evolution suggested that different species developed, one from another, over long periods of time. In 1859 Darwin published The Origin of Species by Means of Natural Select.” Stating the species evolved from other species which are now extinct. This idea outraged those who believed in the biblical account of creation.” The result was bitter controversy that continues to that day.

When Darwin published The Descent of Man he avoided stating that humans were descended from nonhuman forms, but his implications of the theories were clear. Darwin believed that humans and monkeys are descended from a common ancestor who lived long ago Darwinists would further argue that natural selection was the process through which the physical and genetic form of that common ancestor diverged to become both monkey and human. Charles Darwin’s theory of evolution suggested that different species developed, one from another, over long periods of time.

Natural selection is a process we can see at work in the world today. The understanding of natural selection we have today is different from that originally put forward by Darwin. A century and a half of research had added tremendously to the information Darwin had to work with, and entirely new fields, like population genetics, have emerged.

With this new information, we know that Darwin was wrong about some things. For example, it seems clear that natural selection is not always a uniform process, but can jump and starts. Darwin’s ideas were not wrong but incomplete.